1. Field of Invention
The present invention relates to a lamp module and a multi-lamp circuit, and more particularly, to a balanced current lamp module and a multi-lamp circuit.
2. Related Art
Because a cold cathode fluorescent lamp (CCFL) has a high luminance, the CCFL can serve as a light source and be applied to an electronic device, such as a liquid crystal display, to serve as a backlight source.
FIG. 1 is a schematic view showing a driving circuit for a conventional balanced current lamp circuit. As shown in FIG. 1, a power source 11 is electrically connected with a coil 121 of a transformer 12, and two lamps 14 and 16 are respectively electrically connected with the other coil 122 of the transformer 12 through two capacitors 13 and 15. However, this connection method cannot ensure the working currents of the lamps 14 and 16 to be the same, and the luminance of the lamps 14 and 16 is thus different from each other.
Furthermore, FIG. 2 is a schematic view showing another driving circuit with an added balanced transformer. As shown in FIG. 2, a power source 21 is electrically connected with a coil 221 of a transformer 22. Two lamps 24 and 26 are respectively electrically connected with the other coil 222 of the transformer 22 through two capacitors 23 and 25. The lamps 24 and 26 are also electrically connected with two coils 271 and 272 of a balanced transformer 27, such that the working currents of the lamps 24 and 26 are adjusted and unified through the balanced transformer 27.
In addition, a feedback circuit 28 may also be connected with the coil 271 of the balanced transformer 27 so as to control the power source 21 in a feedback manner according to the working current of the lamp 24 and thus to adjust the working currents of the lamps 24 and 26.
Although this connection method can ensure the lamps 24 and 26 to have the same working current, the amount of balanced transformers has to be increased when the amount of lamps is increased because two lamps need one balanced transformer to ensure the working currents of the lamps to be the same. Thus, the cost is increased and the high cost is disadvantageous to the manufacture if the lamps are ensured to have the same luminance.
It is thus imperative to provide a balanced current lamp module and a multi-lamp circuit, which can control and unify the working currents of the lamps, such that the lamps can be held at the same luminance, and the amount and cost of the balanced transformers can be decreased.